Urgent help help help phy Q!

8.The force of gravity does work on a satellite when it is in
a. circular orbit.
b. elliptical orbit.
c. both of these
d. neither of these

9.Planets would crash into the sun if it weren't for
a. the fact that they are beyond the main gravitation of the sun.
b. their vast distances from the sun.
c. the inverse-square law.
d. their tangential velocities.
e. their relatively small masses.

10.Minimal orbit speed about the Earth is about 8 km/s. Minimal orbital speed about Jupiter would be
a. more than 8 km/s.
b. less than 8 km/s.
c. about 8 km/s.

11.Compared to the period of satellites in orbit close to the Earth, the period of satellites in orbit far from the Earth is
a. the same.
b. longer.
c. shorter.
d. not enough information

12.Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity
a. decreases.
b. increases.
c. remains constant.

13.Half way to the center of a planet of uniform density, your weight compared to at the surface would be
a. one-quarter.
b. one-half.
c. three-quarters.
d. the same as at the surface.
e. zero.

14.Which would require the greater energy; slowing down of the orbital speed of the Earth so it crashes into the sun, or speeding up the orbital speed of the Earth so it escapes the sun?
a. same each way
b. speeding up
c. slowing down

15.The period of a satellite, the time it takes for a complete revolution, depends on the satellite's
a. radial distance.
b. weight.
c. mass.
d. all of these
e. none of these